1. Field of the Invention
The present invention relates to improvements in MacPherson strut suspension for automotive vehicle steering road wheels, i.e., front wheels.
2. Description of the Prior Art
MacPherson strut suspension is well known in the art and used in many small passenger cars. A typical example of MacPherson strut suspension is shown in FIGS. 1 and 2. Referring to the drawings, the MacPherson strut suspension is generally indicated at 10 and includes two upright strut assemblies 12 interconnecting front wheels 14 and a vehicle body 16. As shown in FIG. 2, each strut assembly 12 has an outer tube 18 and a shock absorber 20 fixedly received therein. The shock absorber 20 has a piston rod 22 projecting upwardly from the upper end of the strut outer tube 18 to be pivotally and resiliently connected to the vehicle body 16. The strut assembly 12 also has a bracket 24 secured to the lower end of the strut outer tube 18 for supporting a steering knuckle 26. Also secured to the strut outer tube 18 is a lower spring seat 28 for retaining the lower end of a front coil spring 30 placed around the piston rod 22 and the strut outer tube 18. The upper end of the front coil spring 30 is retained by an upper spring seat 32 which has an opening permitting the piston rod 22 to extend upwardly therethrough and is urged by the front coil spring 30 against the vehicle body 16 by interposing therebetween a bearing 34 so that the upper spring seat 32 is rotatable relative to the vehicle body 16. Mounted on the piston rod 22 at a location between the upper spring seat 32 and the upper end of the strut outer tube 18 is a bumper rubber 36 adapted to function as a damper for large shocks. The front wheel 14 is thus turnable about the center axis of the strut assembly 12 together with the strut outer tube 18, the coil spring 30 and so on.
In the above described front suspension, there is provided between the front coil spring 30 and the upper spring seat 32 a spring seat rubber 38 for insulation therebetween. The spring seat rubber 38 has a spring constant which sharply increases with increasing compression force applied thereto. When installed in place, the spring seat rubber 38 is subjected to a relatively large pre-load from the front coil spring 30 and thus given a large spring constant. Such spring seat rubber 38, therefore, cannot sufficiently insulate the vehicle body from shocks, particularly from small vibrations but allows the small vibrations to be transferred through the bearing 34 to the vehicle body 16. The above described MacPherson strut suspension thus has the drawback that it cannot effectively insulate the vehicle body 16 from shocks, particularly from small vibrations, resulting in a deteriorated ride quality. In order to overcome this drawback, the spring seat rubber 38 may be increased in solid thickness or height. This, however, results in another problem of an increased vehicle height.